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In this study, we observed natural methane (CH4) hydrate sediments, which are a type of unconventional natural gas resources, using x-ray computed tomography (CT). Because CH4 hydrates are formed by hydrogen bonding of water molecules with CH4, material decomposition becomes challenging when CH4 hydrates coexist with liquid or solid water in natural sediments. Tri-contrast (absorption, refraction, and scattering) imaging was performed via diffraction enhanced x-ray CT optics using monochromatic synchrotron x rays. The quantitative characterization of the contrast changes successfully enabled the decomposition of CH4 hydrates coexisting with frozen seawater (ice) in natural sediments obtained from the Okhotsk Sea. This study reveals complementary structural information about the microtexture and spatial relation among CH4 hydrates, ice, and pores by utilizing the distinct physical properties of x rays when passing through the materials. These results highlight the exceptional capabilities of high-resolution multicontrast x-ray tomography in materials science and geoscience applications. [ABSTRACT FROM AUTHOR]

To ascertain whether rapid industrialization has affected the accumulation of heavy metals (HMs) in Suzhou Industrial Park (SIP), China, the occurrence and ecological risk of HMs, including Cu, Zn, Pb, Cr, Cd, Ni, As and Hg in sediments were analyzed. The results indicated that total concentrations of HMs (mg kg−1) were in the descending sequence of Zn (235.28) > Cr (95.71) > Cu (78.91) > Ni (55.51) > Pb (23.96) > As (22.12) > Cd (0.38) > Hg (0.14). The concentrations of HMs, except for Ni and Cd, were found to be below the probable effect level (PEL). Correlation analysis (CA) and principal component analysis (PCA) showed that HMs in SIP mainly originated from anthropogenic activities. HMs were mainly in residual fractions (55.5 ~ 95.1%), and the exchangeable fractions of Zn and Cd were relatively high. The risk assessment results indicated that Hg and Cd significantly contributed to ecological risks, whereas Cr and Pb made relatively minor contributions. Our findings indicated that intense anthropogenic activities promote HMs accumulations in streams in SIP during rapid industrialization. [ABSTRACT FROM AUTHOR]

The resting spore stage of Cerataulina bicornis has been reported sporadically from the Indian Sundarbans, with one sediment core record that dates back to ∼2000 yrs. BP, but its vegetative stage has remained elusive during this entire period. The present report of its vegetative stage is a new record from this estuarine system. A comprehensive morphometric description along with molecular data of rbcL and 18s rDNA of the vegetative stage of C. bicornis is presented. The morphological and morphometric characters observed in the light microscope (LM) and scanning electron microscope (SEM) studies, along with a detailed description of the copulae, establish its distinction from other Cerataulina spp. described from different parts of the world. [ABSTRACT FROM AUTHOR]

The processes of reagent and sorption removal of iron ions from water were investigated and the efficiency of deironing was evaluated. Lime and biosorbents based on walnut shells were used through experiments. The range of iron ions concentrations from 2 to 100 mg/L was studied. The efficiency of deironing is reached maximum efficiency during biosorbtion. In order to create resource-efficient technologies, it is important to develop effective methods of sludge and spent sorbents utilisation. The sediments formed as a result of reagent and sorption purification of water from iron were utilised in the composition of cement with the consumption 3%. The effect of additives application in cement production was evaluated according to the following properties: normal density, coefficient of water separation, time of hardening, compressive strength at the age of 2 and 28 days. [ABSTRACT FROM AUTHOR]

Offshore piles are widely used as support and anchoring structures to provide stable support foundations. In this study, a novel torpedo pile is designed that combines water-jet technology and vibration loading to disturb/fluidize the cohesive sediments around the torpedo pile, reduce the resistance between the torpedo pile and cohesive sediments, and increase the efficiency of pile penetration and extraction. Experiments were conducted to investigate the characteristics of pile penetration and extraction in water-jet and vibration loading scenarios. The results indicated that the combined vibration and water jet method significantly reduced the resistance of the cohesive sediment to the torpedo pile during the pile penetration process, and the pile penetration speed increased as the water-jet pressure increased. The extraction efficiency of the torpedo pile was most significantly improved under the combined vibration and water jet method, and the maximum extraction force of the pile was reduced by approximately 78.2%. [ABSTRACT FROM AUTHOR]

New data on the composition and structure of the Jurassic section in the Central zone of the Polousnyi Terrane are presented. The arkosic composition of sandstones and the predominance of granites in the sediment provenance was established by petrographic data. Both redeposited fragments of volcanic rocks of various composition and synchronous pyroclastic material were identified in the sandstones. U–Pb isotope dating of detrital zircons and the obtained maximum depositional age made it possible to revise the stratigraphic volume of the Jurassic sediments exposed in the Central Zone and to limit it from the Upper Bajocian to the Tithonian. The immaturity of the composition and the absence of reliably dated Hettangian–Aalenian sediments indicate a new cycle of sedimentation and contradict the existence of a single Verkhoyansk passive margin in the Triassic–Jurassic. [ABSTRACT FROM AUTHOR]

Gilgit River Basin (GRB) is one of the primary fluvial aquatic systems flowing through Gilgit-Baltistan and a water source for recreation, fisheries, irrigation, and drinking to more than 1.8 million people. This study aimed to investigate heavy metals (HM) contamination levels in sediments of GRB, northern Pakistan. Fifty-five samples were picked from the various sections of GRB and examined for HM concentrations. Fe showed the maximum average concentration of 27,743 mg/kg, while Cd was noted with a minimum average of 1.06 mg/kg. HM concentrations were noted within the world river system guidelines except Cd, which also surpassed the sediment quality guidelines set by USEPA. HM concentrations of GRB sediments were used for the geospatial and ecotoxicological risk indices. Geospatial analyses showed higher levels of HM contamination and risk in the sediments of Ishkomen River in GRB. HM contamination in GRB sediments showed low to moderate levels of risk to exposed aquatic ecosystems. Statistical analyses were used for the HM source apportionment in sediments of GRB, suggesting a major contribution from natural activities. This study recommends seasonal variation in HM contamination of water and sediments studies in the GRB. [ABSTRACT FROM AUTHOR]

Microplastics (MPs), or plastic particles smaller than 5 mm, are emerging contaminants that potentially affect aquatic species and humans. More research has been undertaken in the marine environment; however, rivers that serve as a sink and pathways for plastic entering the ocean have received less attention. The current study investigated the presence of MPs in the sediments of the Cagayan de Oro River, one of the top plastic-emitting rivers listed in the Philippines. Sediment samples were collected from the six sampling stations from upstream to downstream using a Van Veen grab sampler. Through stereomicroscope and Fourier-transform infrared spectroscopy (FTIR), MPs were analyzed and categorized according to color, shape, size, and polymer type. All the sampling stations were contaminated with MPs ranging from 4.4 ± 2.57 to 33.3 ± 4.44 items/kg. The highest density of MPs was found close to the river mouth that drains into Macajalar Bay which suggests that riverine contributions are substantial contributory to MPs contamination in the marine environments. Prevalent types of MPs are blue-colored (41%), fiber-shaped (41%), 0.5–1.0 mm (43%), and polyethylene (43%) particles. Microplastic accumulation is generally higher downstream than upstream. [ABSTRACT FROM AUTHOR]

Flooding water in extreme hydrometeorological events may be significantly contracted by bridge abutments and superstructures, leading to severe sediment scour and threatening structure stability. A series of large-scale laboratory experiments assessing flood-induced scour processes near bridge abutments are presented, with particular attention paid to the dependence of scour pattern on factors such as deck submergence (vertical contraction), abutment/embankment length (lateral contraction), abutment structure, and general bed mobility, which are analyzed based on post-scour transverse bed profiles and the general bed morphology. It is found that the scour hole's depth, geometry, location, and corresponding time dependence are intricately affected by the aforementioned factors and demonstrate very complicated behaviors. The current design criterion of HEC-23 is sufficient to prevent disastrous embankment breaching but cannot avoid channel erosion or abutment toe undercutting in severe floods. The location of the greatest scour may migrate with time during floods and is closely related to the abutment structure and length. Furthermore, the existing scour predictors are examined and compared with recent data sets; more improvements are needed to reflect the complex physical mechanism of scour processes. Finally, a new method for estimating sediment loss is proposed. [ABSTRACT FROM AUTHOR]

In the South China Sea, a significant amount of methane hydrate exists in the sediment containing fine-grained soil. Increasing temperature and/or decreasing pore pressure can remarkably degrade the mechanical characteristics of this methane hydrate–bearing fine-grained sediment (HBFS). In this study, several compression tests under triaxial stress condition on HBFS are performed with changing temperature and pore pressure. The experimental results reveal that the HBFS specimen has an enhanced stiffness and failure strength characteristic under lower temperature and/or higher pore pressure conditions. An improved phase state parameter H is presented as a characterization for the temperature and pore pressure condition, which considers the capillary effect for HBFS with wide pore size distribution. The secant modulus and failure strength tend to linearly increase with the rising improved phase state parameter H. The internal friction angle is independent of the temperature and pore pressure, while the cohesion exhibits a significantly linear increase with the rising improved phase state parameter H. In addition, the shear–dilatancy curve shifts to the right with the rising improved state parameter H owing to the enhanced cementing strength of hydrate–soil cluster. These research findings are beneficial for grasping the mechanical behavior of HBFS. Furthermore, this research also provides data support for building the constitutive model of HBFS during methane hydrate recovery. [ABSTRACT FROM AUTHOR]

This work presents a spatial and temporal distribution of tributyltin (TBT) and TBT pollution assessment of the Croatian Adriatic coast in the period 2016 - 2023. The monitoring of TBT pollution was carried out within the Water Framework Directive (2000/60/EC) and the Marine Strategy Framework Directive (2008/56/EC). TBT concentrations were measured at 63 sites in coastal and transitional waters in three compartments - water, sediments and mussels. The ranges of TBT concentrations were <0.06 - 6.40 ng(TBT)/L in the water column, <1 - 2546 ng (TBT)/g(d.w.) in sediments, and <1 - 655 ng(TBT)/g(d.w.) in mussels, while transitional waters were in general more polluted than coastal waters. Monitoring of TBT concentrations in water showed that 30% of monitored sites were continuously polluted with TBT with average annual concentrations exceeding AA-EQS [0.2 ng (TBT)/L], while 20% of the sites had concentrations in sediments above the proposed EQS for sediments [1.6 ng(TBT)/g(d.w.)]. In mussels, TBT was detected at 70% of the sites with more than 60% of the sites exceeding the OSPAR criteria [12.6 ng(TBT)/g (d.w.)], indicating that the occurrence of imposex in gastropods at these sites is very likely. Only a slight decrease in TBT levels was observed over the investigated period, but concentrations at most contaminated sites did not fall below the EQS. This study shows that, despite the ban of TBT-based antifouling paints more than 15 years ago (except for public and military vessels), contamination of the Croatian Adriatic coast with TBT still exists and regular monitoring is essential. The TBT distribution was primarily determined by the vicinity of the pollution source, i.e. shipping traffic, but the role of physicochemical parameters, such as dissolved organic carbon (DOC) and transparency of the water column, should not be disregarded as well as the influence of hydrodynamics in the transitional waters. Although monitoring of TBT concentrations in water is an established approach to assess recent pollution, this long-term study has shown that mussels can be the most reliable indicator of pollution in a given area over the last several months. [ABSTRACT FROM AUTHOR]

Pollution of the natural environment by microplastics has become a global issue in ecosystems as it poses a potential long‐term threat to biota. Microplastics can accrue in high abundances in sediments of aquatic ecosystems while also contaminating pelagic filter feeders, which could transfer pollutants up trophic webs. We assess the abundance and distribution of microplastics in benthic sediments and Cladocera taxa in a subtropical Austral reservoir using a combination of geospatial techniques, physicochemical analyses, diversity indices, and multivariate statistics between two seasons (i.e., hot–wet and cool–dry). We found particularly high densities of microplastics during the cool–dry season for both sediments (mean 224.1 vs. 189 particles kg–1 dry weight) and Cladocera taxa (0.3 particles per individual). Cladocera microplastic shapes were dominated by fibers with high densities of the transparent color scheme. Pearson correlation results indicated that sediment microplastic abundances were negatively correlated with chlorophyll–a concentration, temperature, and resistivity, whereas they were positively correlated with pH and salinity during the hot–wet season, with no variables significant in the cool–dry season. Cladocera microplastic abundances were positively correlated with conductivity and salinity during the cool–dry season, but no variables in the hot–wet season. These findings provide insights into the role of reservoirs as microplastic retention sites and the potential for uptake and transfer from lower trophic groups. These insights can be used to strengthen future monitoring and intervention strategies. Integr Environ Assess Manag 2024;20:2256–2270. © 2024 SETAC Key Points: Sediments and Cladocera taxa were dominated by fibers.The distribution of microplastic types varied across sites.The density of microplastics in Cladocera taxa was significantly high.Cladocera may transfer microplastics to other aquatic organisms. [ABSTRACT FROM AUTHOR]

The research on the source of marine sediments has a vital impact on identifying material sources, transport mechanism, and the evolution of sedimentary environments. Previous studies have shown many outstanding achievements on the source analysis of the South China Sea, but there are still some controversies over the complex source and transport mechanisms of the Zhongjiannan Basin. In this study, we took a gravity core (583cm) from the Zhongjiannan Basin and analyzed the particle size, rare earth elements, and Sr-Nd isotopes of the core sediments to further reveal the source and transport mechanism. The surface sediments in the Zhongjiannan Basinwere relatively stable, with an average particle size ranging from 5.66 to 17.74 mm. The normalized standard curve of chondrite exhibited the depletion of Eu, with LREE dominated in REE. As the depth increased, 87Sr/86Sr ratios showed a gradually increasing trend, while dNd change was relatively complex. On the whole, 87Sr/86Sr ratios (from 0.721537 to 0.725322) and dNd (from -11.561617 to -12.289374) were in a relatively narrow range. Based on the particle size characteristics, we found the geochemical characteristics of sediment largely resulted fromdifferent sediment sources. By comparing rare earth elements and Sr-Nd isotopes, we concluded the sediment of the Zhongjiannan Basin was from mainly terrigenous contribution. In addition, taking into account factors such as terrain, migration distance, and river drainage system, we conclude the sediment were mainly from the Mekong River, the Red River, Taiwan Island, and Hainan Island. The surface current along the northeast direction was the main transportation route for the sediments of the Mekong River. The Guangdong coastal current and the southwest surface current transported sediment from the Red River and Hainan Island to the Zhongjiannan Basin. The surface current and deep-water current in the southwest direction carried sediment from Taiwan Island to the study area, while the Kuroshio also had some impacts on the sediment transportation of Taiwan Island. This study has reinforced the research on provenance in the South China Sea Basin and has an important significance on evolution of sedimentary environments, evolution of ancient oceans. [ABSTRACT FROM AUTHOR]

Fluvial cross strata are fundamental sedimentary structures that record past flow and sediment transport conditions. Bedform preservation can be significantly influenced by the presence of larger‐scale topographic features that cause spatial gradients in flow. However, our understanding of the controls on cross strata preservation in the presence of a morphodynamic hierarchy is limited. Here, using high‐resolution bathymetry from a physical experiment, we quantify bedform evolution and cross strata preservation in a zone of flow expansion and deceleration. Results show that the size and celerity of superimposed bedforms decreases along the host‐bedform lee slope, leading to a systematic downstream increase in the sediment accumulation rate relative to bedform celerity. This increase in local bedform climb angle results in the preservation of a larger fraction of formative bedforms. Our results highlight the need to revise current paleohydraulic reconstruction models, and demonstrates that fluvial morphodynamic hierarchy is a fundamental determinant of sedimentary strata. Plain Language Summary: Dune evolution in rivers creates inclined layers of sediment, called cross strata, that are an integral part of the rock record on Earth and Mars. The thickness distribution of cross strata is the primary means of estimating ancient flow and sediment transport conditions. Dunes exist with larger‐scale features, such as bars and larger dunes, in rivers, where a train of dunes responds to flow steering by larger‐scale features through changes in dune size and speed. However, we currently lack data to assess the influence of larger‐scale features on dune evolution and cross strata. Here, we studied dune evolution on the lee side (downstream facing slope) of a larger bedform in an experimental channel, where flow expands and slows down. Using high‐resolution data, we show that the dune size and speed decrease with downstream distance along the host‐bedform lee side. The rate of sediment build‐up relative to dune speed increases downstream, which leads to the preservation of a larger fraction of dunes in cross strata. Results suggest that cross strata preserved in the presence of larger‐scale features are common in the rock record, and we need to revise our current models for estimating past flow conditions from cross strata. Key Points: We characterize bedform evolution and cross strata preservation in a zone of flow expansion and deceleration in a physical experimentBedform size and celerity decrease along the host‐bedform lee slope, causing an increase in aggradation rate relative to bedform celerityA larger fraction of the formative bedforms is preserved as cross strata than typically assumed by paleohydraulic reconstruction models [ABSTRACT FROM AUTHOR]

Heavy metal contamination is a serious global issue that threatens both environmental and human health. This study investigated the levels of 12 heavy metals in sediments, roots, stems, and leaves of Phragmites australis (common reed) from a river in Iran, using an inductively coupled plasma optical emission spectrometer (ICP-OES). The sediment metal concentration order was: Aluminum (Al) > Iron (Fe) > Manganese (Mn) > Zinc (Zn) > Magnesium (Mg) > Nickel (Ni) > Chromium (Cr) > Lead (Pb) > Copper (Cu) > Arsenic (As) > Vanadium (V) with Cadmium (Cd) below detection limit. Concentrations of As, Ni, Pb, and Zn in the sediments exceeded background values. According to sediment quality guidelines (SQGs), metal concentrations were between the threshold effect level (TEL) and the probable effect level (PEL), remaining below the severe effect level (SEL), except for Ni. Average metal concentrations in plant tissues were lower than in sediment samples, with roots showing higher levels of Cd, V, Cu, Pb, Zn, As, Al, Mg, and Fe than in the shoots, while leaves had higher Ni, Cr, and Mn. The bioaccumulation factor of less than 1 (except for V) indicates limited bioavailibility of these metals. [ABSTRACT FROM AUTHOR]

ABSTRACT Fieldwork investigations and stratigraphic analyses in the Parnaíba Basin, northern Brazil, reveal the interaction of the uppermost part of the Triassic Sambaíba aeolian dune field (erg) system with the latest Triassic–earliest Jurassic Mosquito lava flows. The lava flows originated as part of the Central Atlantic Magmatic Province (CAMP, ~201 Ma) and covered the aeolian system, allowing almost complete preservation of large‐scale in situ aeolian bedforms, even preserving lee‐ and stoss‐side. During the emplacement, the lava flows interacted with unconsolidated aeolian sediment, generating sediment–lava deformation features that are preserved at the interface between these units. This occurrence attests to arid conditions in the low latitudes of Gondwana at the Triassic–Jurassic transition. [ABSTRACT FROM AUTHOR]

The non-uniform suspended sediment flowing into the Yangtze River Estuary (YRE) has a substantial impact on riverbed evolution and the ecological environment. Conducting a numerical simulation can provide missing measurement data and act as an important support for river management. In this study, we developed a formula for determining the non-uniform suspended sediment-carrying capacity (SCC) based on the statistical theory of sediment transport. The formula was applied to a river network model domaining the tidal section of the lower reaches of the Yangtze River (LYR) to simulate the non-uniform suspended sediment flowing into the YRE. The verification results showed that the model accurately simulated fine-grained sediments with a high measurement accuracy. The simulation results for coarsegrained sediments were consistent with riverbed evolution thatmanifests as erosion. Owing to the sediment transport complexity in natural rivers, we propose a method for optimizing calculations of the SCC that providesmore accuratemodeling results and can be adapted when the observational measurement accuracy is improved in the future. These findings provide support for simulations and measurements of non-uniform suspended sediment transported in the LYR. [ABSTRACT FROM AUTHOR]

The Engineering Ocean Seismic 3D system, which enables ultra-high-resolution seismic surveys on a smaller survey scale, was deployed in Yeongil Bay, Pohang, South Korea. The region is renowned for abundant shallow gas deposits and faults. Based on acoustic impedance contrast and abnormal behavior observations, two seismic anomalies termed channel and polka-dot anomalies have been identified in the seismic volume. Seismic attribute analysis based on the signal amplitude and structural characteristics reveals that these anomalies correspond to shallow biogenic gas deposits. Structural interpretation of the seismic volume revealed that the contractional deformation resulting from post-Miocene neotectonics has resulted in uplift and reverse faulting in the Pohang region, contributing to the formation of anomalies. The channel anomalies correspond to gas-saturated tidal channels that formed during eustatic sea-level changes in the post-Last Glacial Maximum period. The polka-dot anomalies are located in topographic lows and are overlain by neotectonic sediment. The different behaviors of these anomalies in a seismic volume can be attributed to the different thicknesses of overburden overlying each of the anomalies. [ABSTRACT FROM AUTHOR]

ABSTRACT The northern continental margin of the South China Sea (SCS) is an important component of deep‐water circulation, providing excellent conditions for studying bottom currents in a marginal sea. Seismic data were employed to discern the sedimentary patterns prevalent in the deep‐water continental slope sediments on the northern continental margin of the SCS, encompassing gravity flow, contourite and mixed depositional systems. The contourite depositional system includes various types of deposits (such as separated mounded drifts, patch or channel‐related drifts, deformed sheeted drifts, composite drifts, bottom current sediment waves, plastered contourite drifts) and various morphologic erosional features eroded by the bottom current (such as moats, non‐depositional surfaces, troughs and scarps). These contourite features are related to the continental slope's morphology and its sources. The Dongsha slope exhibits distinctive characteristics marked by intense bottom current erosion and deposition, featuring separated mounded drifts and deformed sheeted drifts along its lower slope. The lower slope of the Pearl River showcases a spectrum of bottom current‐induced features, including sediment wave fields, erosion fields and contourite drifts. The southern flank of the Shenhu slope is characterised by a bottom current erosion field, a non‐depositional surface, a sediment wave field and isolated mounded drifts. On the Yingqiong slope, the contourite drifts are limited to its southern flank where gravity flow action is absent, and the complex geomorphology interacts with the bottom current, forming a complex contourite depositional system. The results of this study serve as a foundational framework for further global research on bottom current circulation and hydrodynamics. [ABSTRACT FROM AUTHOR]

Notch development at the base of sea cliffs is an important control on cliff recession rates, but a detailed mechanistic understanding of notch formation by swash abrasion is lacking. We conducted physical experiments, using homogeneous erodible rock simulants, to study notch‐forming mechanisms under periodic sediment‐laden bore impacts. Our findings reveal shifts in the temporal dynamics of notch development. Initially, swash uprush and vortex formation contribute to a positive feedback loop that creates a shallow and wide notch. Subsequently, upward erosion ceases, and notch backwear and downwear are dominated by the vortex. Eventually, sediment deposition armors the notch floor; this negative feedback loop reduces erosion. The sediment size determines the amount of erosion, with a range of grain sizes generating maximum erosion. This indicates a dependence on the momentum of the sediment particles entrained within the bore. This research reveals fundamental notch formation mechanisms driven by swash abrasion. Plain Language Summary: When waves attack a rock cliff, they gradually undercut the cliff and remove materials, forming a wave‐cut notch. Studying how notches form and develop in natural settings takes a very long time, so we created a weaker cliff in the laboratory using easily eroded foam. The cliff was exposed to repeated impacts from bores carrying sediment, representing the impact of broken waves. Notch formation is observed over a few hundred hours. Initially, the notch is wide and shallow. As it grows, abrasive sediment cannot be propelled into the roof, stopping the upward expansion of the notch, and sediment piles up at the bottom, blocking further downward erosion. The notch continues to deepen, but at a decreasing rate. The size of the beach sand or gravel has an important influence on the erosion rate. If the sediments are too large or too small, little erosion occurs, whereas sediments of a certain size can cause rapid erosion. This is because waves need to be able to entrain sediment and hurl it with sufficient force against the cliff to cause erosion. Key Points: Controlled laboratory experiments with repeated swash impacts reveal positive and negative feedback mechanisms in abrasion notch formationNotch geometry varies over time and is determined by swash impact location, vortex formation and sediment depositionGrain size modulates beach shape and sediment‐laden bore momentum, collectively influencing notch development [ABSTRACT FROM AUTHOR]

With the development of cage culture, increasing heavy metals concentrations are being taken into sediments. The accumulation of heavy metals in sediments may cause long term environmental issues and pose threat to human health. Fourteen surface sediment samples were collected to assess the contamination status and potential ecological risk of heavy metals, and identify their potential sources from the cage fish farm of Poyang Lake. The concentrations of Cu, Pb, Zn, Cd, Cr, As and Ni in the sediments were measured by ICP-MS. The geo-accumulation index, enrichment factor and potential ecological risk index were implied to evaluate their pollution levels and ecological risk. The principal component analysis was used to identify their potential sources. The results showed that all of the examined heavy metals content exceeded their background values. These heavy metals (except Cd, Cr and As) presented moderately polluted level. Cu showed significant enrichment, Zn, Pb and Ni exhibited moderate enrichment, As and Cd presented minimal enrichment. Cu and Cd posed a moderate ecological risk, and the other heavy metals posed a low ecological risk. The comprehensive potential ecological risk was associated with considerable ecological risk. Cage culture, smelting, mining and agriculture activities were their primary pollution sources. [ABSTRACT FROM AUTHOR]

Sediment transport is a geophysical phenomenon characterized by the displacement of sediment particles in both the horizontal and vertical directions due to various forces. Most of the sediment transport equations currently used include only parameters related to the horizontal direction. This study measured both instantaneous longitudinal and vertical parameters, i.e., velocities and forces, and found that the magnitude and direction of the vertical force play an important role in sediment incipient motion. An innovative experimental system was developed to investigate the effect of vertical force on incipient motion in rapidly varying flows. A quadrant analysis of the instantaneous measured forces on the critical shear stress was performed. The research revealed that upward positive vertical forces enhance particle mobility, whereas downward negative vertical forces increase particle stability. Novel equations have been developed to represent the influence of vertical forces on sediment transport. A comprehensive critical Shields stress for sediment transport was proposed, extending the Classic Shields diagram to encompass the incipient motion in highly unsteady flows. [ABSTRACT FROM AUTHOR]

In the longstanding development of hydrate-bearing sediment (HBS) reservoirs, slow and permanent deformation of the formation will occur under the influence of stress, which endangers the safety of hydrate development projects. This paper takes hydrate-bearing sandy sediment (HBSS) as the research object and conducts triaxial compression creep tests at different saturation degrees (20%, 30%, and 40%). The results show that the hydrate-containing sandy sediments have strong creep characteristics, and accelerated creep phenomenon will occur under the long-term action of high stress. The longstanding destructive power of the specimen progressively raises with the increase in hydrate saturation, but the difference in the triaxial strength of the specimen progressively increases. This indicates that the damage to the hydrate structure during long-term loading is the main factor causing the strength decrease. Further, a new nonlinear creep constitutive model was developed by using the nonlinear Burgers model in series with the fractional-order viscoplastic body model, which can well describe the creep properties of HBSS at different saturation levels. [ABSTRACT FROM AUTHOR]

Fallen leaves and their decomposition directly deposit leaf wax n-alkanes into sediments, which can be used to identify local flora. These n-alkanes are important for studying past vegetation and climate, but their distribution in sediments must be known. Aeolian sand n-alkanes are particularly important for understanding paleoclimates in arid regions, despite the challenges of extraction due to their extremely low abundance. To investigate the preservation of plant leaf wax n-alkanes in deserts, we analyzed n-alkanes in aeolian sands from the Northern Ulan Buh Desert (UBD), China, and compared them to the surrounding vegetation. We calculated the total n-alkane concentration (ΣALK), average chain length (ACL21–35), and carbon preference index (CPI21–35). In the Northern UBD, aeolian sand n-alkanes have lower ΣALK, indicating microbial degradation. The eastern aeolian sand has lower CPI21–35 and ACL21–35 than the adjacent vegetation, whereas the western sand values are consistent with the plants, likely due to the transport of plant-derived materials by wind and water from the nearby mountains. Our study shows that sedimentary n-alkane signatures are not only determined by local vegetation but also influenced by environmental factors like temperature and precipitation. Additionally, local deposition processes play a significant role in determining the properties of these n-alkanes. [ABSTRACT FROM AUTHOR]

Sediment erosion poses a significant challenge for hydraulic turbines in sediment-laden rivers. This paper investigates the erosion patterns in high-head Francis turbines using numerical simulations. It analyzes how sediment concentration, particle size, and operating conditions affect wear on turbine components. The results identify the trailing edges of the guide vanes, the intersection of runner blade trailing edge, and runner band as primary erosion zones. Higher sediment concentrations increase erosion intensity and extend the erosion range upstream. Small particles uniformly affect both pressure and suction sides of the blades, while larger particles concentrate erosion near the runner band trailing edges. The flow rate has a greater impact on runner blade erosion than water head, with lower flow rates reducing pressure side erosion but initially increasing, then decreasing suction side erosion. Additionally, the study proposes a multi-objective, multi-condition optimization design method that balances erosion resistance and energy efficiency. The optimized runner reduces the maximum erosion rate by 23.91% while limiting the weighted efficiency loss to under 0.1%. The improved runner design reduces high erosion areas on both blade sides, particularly decreasing particle impact speeds near the trailing edges. Sensitivity analysis reveals a trade-off between minimizing erosion and maintaining hydraulic efficiency, highlighting the importance of span height at 75% for controlling erosion. Changes in blade circumference angle generally reduce erosion but may also lower efficiency. Overall, this research demonstrates a successful reduction in Francis turbine erosion while preserving hydraulic efficiency, offering valuable guidance for anti-erosion turbine design in sediment-heavy environments. [ABSTRACT FROM AUTHOR]

Due to the high sand content and hardness in the Kezilesu River Basin, the high-head Francis turbines operating in this basin experience significant issues of guide vane erosion. By altering the skirt structure through varying guide vane height to skirt maximum diameter ratio Δ, the anti-abrasion design of turbine guide vane can be improved. The sand-water velocity, local sediment concentration distribution, and sediment erosion at the surface of a 250 m turbine in a power station within this basin were numerically analyzed under different Δ and operating conditions. The study investigated the influence of different Δ on the wear of the turbine guide vane. The numerical calculations of sand-water flow and sediment erosion in the turbine revealed that under rated working conditions, an optimal Δ = 1.511 was obtained. The sand and water flow remained stable, with low sediment concentration near the skirt. The maximum velocity of sand and water at the skirt wall was lower compared to other Δ conditions, i.e., approximately 45 m/s, and the weighted wear area was only 1057 mm2. Under low flow conditions, an optimal Δ = 1.511 was obtained, with the sediment concentration near the skirt gradually increasing with an increase in Δ. Additionally, the maximum velocity at the skirt wall was about 60 m/s under both conditions. The ratio Δ and the erosion resistance of guide vanes initially increased and then decreased. The research results offer a technical basis for the anti-abrasion design of the guide vane in high-head Francis turbines operating in high hardness, sandy waters. [ABSTRACT FROM AUTHOR]

This study presents a modified stochastic diffusion particle tracking model (MSDPTM) that incorporates energy cascade theory to more accurately simulate suspended sediment transport. The impact of turbulent eddies on sediment particles is an intermittent process, which is also considered in this study. The study examines the time correlation between eddies using eddy turnover time and finds that closer-scale eddies exhibit higher correlations than those farther apart. The statistical properties of particle movement, such as the ensemble mean and variance of particle trajectories, have been calculated and compared with the stochastic diffusion particle tracking model (SDPTM) results. Notably, MSDPTM with intermittency demonstrates a significantly larger ensemble mean of particle trajectories in the streamwise direction than other particle tracking models. The proposed model is validated through comparison with available data, showing its enhanced performance. The results of the simulation indicate that MSDPTM outperforms SDPTM, especially when the intermittency effect of eddies is considered. [ABSTRACT FROM AUTHOR]

Pelton turbines functioning in sandy river environments often encounter difficulties due to the swift movement of sediment particles, leading to erosion and damage to overflow components. These challenges can result in operational instability, particularly noticeable in large turbines. Pressure pulsation is crucial for turbine stability, and alterations in overflow component profiles caused by sediment erosion can worsen pressure pulsations. This study utilizes numerical simulations to analyze turbine pressure pulsations based on surface profile changes of runner buckets after 2 and 4 years of sediment erosion in a single 500 MW large‐scale Pelton turbine. Our findings reveal that erosion leads to a gradual decrease in pressure pulsation along the bucket's splitting edge from the notch to the root. After 4 years of erosion and wear, the relative pressure pulsation amplitude in the root region increased by more than 530%. Additionally, changes occur in the thickness of the water film in the erosion area on the working surface, disrupting the flow pattern and generating more vortices. This occurrence intensifies the relative pressure pulsation amplitude and reduces bucket stability. The study findings highlight the significant impact of sediment erosion on Pelton turbine pressure pulsation, posing a considerable risk to the unit's operational stability and safety. [ABSTRACT FROM AUTHOR]

On continental margins, sediments cause significant and spatially variable delays in seismic phase arrival times. The strong impedance contrast of the sediment‐bedrock interface causes P‐wave splitting that is clearly seen on distributed acoustic sensing recordings of earthquakes, resulting in additional phase arrivals that must be picked separately. We introduce sediment corrections to correctly account for those additional phases in the hypocenter localization procedure. Conceptually, the sediment correction method differs from the commonly‐used station corrections; instead of introducing a mathematically optimal constant time delay for each station and each phase, the corrections are derived from a physical, first‐order modeling of the wave propagation in the sediments. To calibrate the sediment corrections, a two‐step procedure is adopted: (a) the delay between the P‐phase and the converted Ps‐phase is taken as a proxy of the sediment thickness; (b) the P‐ and S‐wave speeds are determined through inversion. We show that sediment corrections are able to account for most of the observed bias while considerably reducing the number of free parameters compared to classical station correction. Moreover, the observed local delays are almost fully explained by the presence of the sedimentary layer, rather than by the 3D velocity variations of the bedrock. We retrieve vP ${v}_{\mathrm{P}}$ and vS ${v}_{\mathrm{S}}$ values that are compatible with values commonly found for sediments. Given the simplicity and physical foundation of the proposed method, we recommend the use of sediment corrections over station corrections whenever significant P‐wave splitting can be observed. Plain Language Summary: Loose sediments on the ocean floor strongly affect how seismic waves travel from the earthquake hypocenter to the surface. The most important effect is that sediments slow down the seismic waves, causing them to arrive later at the seismic instruments. These delays can make it difficult to accurately locate the source of earthquakes. This study proposes a new method called sediment corrections. We used the distributed acoustic sensing technology to track delays caused by sediment along a telecommunication cable offshore central Chile, located in a very active subduction zone. Using a simple physical model of how seismic waves travel through sediments, we recovered the main structural features of the sediments beneath the cable. Using the properties of the sediments, we then improved the localization of the earthquake sources. Importantly, this method has the potential to be applied in different sedimentary environments, reducing the challenges associated with interpreting data collected in such geological areas. Key Points: We propose a novel inversion method to account for the presence of shallow sedimentary layers in hypocenter localizationThe inferred sediment properties explain the travel time discrepancies compared to the regional velocity modelThe sediment correction method improves hypocenter localization efforts with a small number of free parameters [ABSTRACT FROM AUTHOR]

Mercury, a trace metal, is a persistent environmental pollutant that can be detected even in remote regions, including high-mountain lakes. This study examined mercury concentrations in the sediment of two lakes in the French Pyrenees, the Legunabens and Labant lakes. Sediment samples were collected using a Hon-Kajak Sediment Corer, and mercury concentrations were measured following the EPA 7473 method with a direct mercury analyzer (DMA-80). Mercury levels reached up to 283 ng g−1 in the Legunabens lake and up to 110 ng g−1 in the Labant lake, possibly linked to the mining history of the Ariège department and atmospheric deposition from distant sources. These findings indicate significant contamination, ranging from an 8% to 42% probability of generating adverse biological effects according to Canadian standards, and approximately 90% higher concentrations compared to average mercury concentrations in other Pyrenean lakes. Such contamination poses potential risks to aquatic life and the environment due to mercury's toxicity and bioaccumulation in microorganisms. [ABSTRACT FROM AUTHOR]

Submerged plants and related disturbances can affect both the phosphorus (P) release and the microbial communities in sediments. In this study, a sediment resuspension system was constructed, and P variability characteristics influenced by Vallisneria natans (V. natans) and the response mechanism of the microbial community were studied. The results indicated that the total phosphorus (TP) content increased from 678.875 to 1019.133 mg/kg and from 1126.017 to 1280.679 mg/kg in sediments and suspended solids (SSs) during the sediment resuspension process, respectively. Organic P (OP) increased by 127.344 mg/kg and 302.448 mg/kg in sediments and SSs after the disturbance, respectively. The microbial communities in the sediments and the leaves of V. natans had higher Chao values after the disturbance, while Shannon values decreased after the disturbance compared to the control in SSs. Proteobacteria had the highest abundance with the value of 51.1% after the disturbance in the sediments and SSs, and the abundance values of Proteobacteria in rhizomes and leaves of V. natans could reach 73.2% on average. Chloroflexi, Acidobacteria, and Firmicutes were also the main phyla in the sediment resuspension system. Sodium hydroxide extractable P (NaOH-P) in sediments could reduce the bioavailability of this P fraction under disturbance conditions. The decrease in the abundance of Bacteroidetes and Nitrospirae indicated that they were more sensitive to the disturbance, and the rotational speed changed the survival conditions for the Bacteroidetes and Nitrospirae. The response mechanism of microbial community during the sediment resuspension process could reflect the influence of the microbial community on the changing characteristics of P and could provide a theoretical foundation for P control at the micro level. [ABSTRACT FROM AUTHOR]

The principal aim of this paper is to present a critical overview of the stratigraphical subdivision and correlation of the Late Mid‐Pleistocene (LMP) sediments in Lithuania. In recent decades, a number of studies of LMP sediments have been carried out, allowing clarification of the stratigraphical position of individual sedimentary sections. Particular efforts have been made to determine the age of sediments using a variety of absolute age determination methods. However, there are still several outstanding questions. It is still unclear how many warm periods occurred during the Saalian in Lithuania and of what magnitude. The least problematic issue is identification of the Butėnai (Holsteinian) Interglacial as it correlates well biostratigraphically with the contemporaneous sections of adjacent areas. The most controversial unit is the Snaigupėlė Interglacial, the age of which continues to be a subject of debate. Recently, more evidence has emerged that the sediments considered to be of the Snaigupėlė Interglacial are contemporaneous with the Merkinė (Eemian) Interglacial. The chronological placement of these sediments closely hinges on the unresolved stratigraphical classification of the Medininkai deposits (MIS 6 or MIS 8?) and the Žemaitija tills (MIS 8 or MIS 10?). The debate is centred on whether these two tills were formed during two entirely different glaciations or represent different phases of a single major glaciation event. Traditionally, these two tills were attributed to distinct glaciation events separated by the Snaigupėlė Interglacial. However, no sedimentary sections have been discovered that contain both these tills and the interglacial sediments that separate them. Given the similar lithological, geochemical and petrographic composition of the Medininkai and Žemaitija tills some research has supported their possible stadial rank. The clarification of these stratigraphical issues in the future may be facilitated by the application of new proxies and re‐examination of the existing LMP key sections. [ABSTRACT FROM AUTHOR]

The shear-wave velocity (Vs) of soils has been acknowledged among the most critical factors affecting the nature of seismic surface motions, known as seismic site effects, in the course of probable earthquakes. Together with the one-dimensional (1D) Vs profiles of soils, the lateral heterogeneity of velocity contrasts may strongly impact seismic ground motions within the surface. Such conditions seem to occur in the city of Tehran, Iran, mainly in the eastern part, Hakimiyeh Valley, wherein alluvial deposits have been settled between the Alborz and Sepayeh (the Anti-Alborz) mountain ranges. In this resepct, the significant differences observed between previous analytical and empirical studies doubles the necessity of estimating real bedrock depth and Vs structure in this area. Given that the improper analysis of seismic site effects, using unrealistic dynamic characteristics, gives rise to the low-accuracy prediction of seismic hazards as well as significant human and financial losses; this study is an attempt to extract the two- dimensional (2D) Vs structure of the subsurface layers in the form of two north-south and east-west profiles, through the single-station and array measurements of ambient noises (viz., microtremors), as the first deep alluvial models in this area. For this purpose, the ambient noises are recorded with reference to 4 and 11 array and single-station measurements, respectively. A circular layout, comprised of two concentric circles, is further considered for the array measurements with 11 three-component narrow-band seismometers, Lennartz LE-3D/20S, within each array. The recorded array seismograms are then analyzed via the spatial autocorrelation (SPAC) method and the frequency-wavenumber (F-K) analysis, and all seismograms recorded in this line are subsequently evaluated by the time-frequency analysis (TFA) of ellipticity in the Geopsy software. Afterward, the results are utilized as the objective functions (OFs) in the inversion operation for calculating the Vs profiles at the selected stations. The neighborhood algorithm is further applied for the inversion of the OFs and the extraction of the Vs profiles. The study results as it comes to the extraction of the 2D profiles and the recognition of the Vs structure in this area, along with the velocity of 2200 m/s, correspond to the seismic bedrock located in the deepest part of the sedimentary basin, 800 m. Moreover, the underground topographies, such as faults, can be identified in the Vs profiles by means ofusing the ambient noises. As a final point, the profiles indicate that the variations in the Vs and dynamic properties of the soil are significant in this area, as one with a complicated subsurface structure. The dominant frequencies of the sediments in Hakimiyeh Valley, reported in previous analytical research, are also significantly different from that those extracted in this empirical study. As an illustration, no sharp and clear peaks can be spotted in the analytical amplification functions in Hakimiyeh Valley, while there are distinct peaks below 2 Hz at most stations in the present study. Furthermore, the study results are in good agreement with the geology of this area, and pave the ground for analytical site effect studies in the future. [ABSTRACT FROM AUTHOR]

Oxygenated deep-sea pelagic sediments with Fe-Mn-oxide particles represent a key oceanic oxic sink for transition metals in the modern ocean. However, the isotopic composition of authigenic Zn in the pelagic zone remains poorly constrained, which hampers our understanding of the global budget of Zn isotopes. Here, we analyzed the Zn isotopic compositions of two deep-sea pelagic sediment columns collected from the Pacific Ocean. The results show that authigenic Zn in deep-sea sediments is primarily hosted by the Fe-Mn (oxyhydr)oxides. The light Zn isotopic signatures (δ66Zn: -0.02‰ to 0.34‰, n = 42; computed as the per mille deviation of the 66Zn/64Zn ratio from the JMC-Lyon standard) observed in deep-sea sediments are completely different from the previously assumed values of ~1.0‰ based on the Zn isotopic compositions of Fe-Mn crusts and nodules. Based on this observation (Zn flux of deep-sea sediments = 5.3 x 108 mol yr-1), we propose a new, balanced global budget for Zn isotopes. [ABSTRACT FROM AUTHOR]

Tournaisian-age failure of marginal lacustrine sediments, and their bulk collapse into an inland rift-basin lake in the Moncton Subbasin, Canada, led to the entrainment of rare, almost complete, three-dimensionally preserved non-woody trees. Preservation of these unique fossils from the Albert Formation was a consequence of contemporaneous seismicity. Synsedimentary structures include an array of soft-sediment deformational features and a field of cross-cutting sand boils indicating multiple seismic shocks >4.6 Mw. This tectonically controlled event, entombing trees whose novel growth form is both evolutionarily and ecologically transitionary and unlike other Paleozoic plants, is a one-off in the paleobotanical record. [ABSTRACT FROM AUTHOR]

Scientific ocean drilling cores recovered years ago (legacy cores), especially as recovered by rotary drilling, commonly show incomplete recovery and core disturbance. We present a novel method to date such cores by presenting the first high-precision U-Pb zircon ages targeting the duration of the Miocene Climate Optimum (MCO; ca. 17-14 Ma) from volcanic ashes at Ocean Drilling Program Site 1000 (on the Nicaragua Rise in the Caribbean Sea). We place these ages within a newly developed framework to address incomplete core recovery and use them to calibrate a high-resolution bulk carbonate δ13C and δ18O record. Our Site 1000 ages show that volcanism of the Columbia River Basalt Group (CRBG) large igneous province was coincident with the interval of greatest sustained MCO warmth at this site. However, if the CRBG were the primary driver of the MCO, our chronology may allow for outgassing preceding volcanism as a major source of CO2. We thus document a promising new way to obtain highly resolved, accurate, and precise numerical age models for legacy deep-sea sediment cores that does not depend on correlation to other records. [ABSTRACT FROM AUTHOR]

Bacterial communities in river sediments are shaped by a trade-off between dispersal from upstream or nearby land and selection by the local environmental conditions. In temporary rivers (i.e. those characterized by long drying periods and subsequent rewetting) seasonal hydrological dynamics shape bacterial communities by connecting or disconnecting different river habitats. In this study, we tracked and compared the temporal and spatial changes in the composition of bacterial communities in streambed sediments and floodplain habitats across both permanent and intermittent river segments. Our findings revealed that environmental selection played a key role in assembling bacterial communities in both segments. We argue that distinct environmental features act as filters at the local scale, favoring specific bacterial taxa in isolated pools and promoting some typically terrestrial taxa in dry areas. Considering the prospective extension of drying intervals due to climate change, our results suggest an emerging trend wherein bacterial assemblages in temporary streams progressively incorporate microorganisms of terrestrial origin, well-adapted to tolerate desiccation phases. This phenomenon may constitute an integral facet of the broader adaptive dynamics of temporary river ecosystems in response to the impacts of climate change. [ABSTRACT FROM AUTHOR]

The abandonment of stone quarries establishes a quarry lake ecosystem that includes soil, water, fish, and vegetarian cover. The activity concentrations (ACs) of natural radionuclides in the waters of several quarry lakes worldwide have not been investigated. In addition, the features of radionuclides, such as distribution, seasonal variability, and health risks, have not been studied. In this study, the ACs of 226Ra, 234U, and 238U were measured in a typical quarry lake in Vietnam with an area of approximately 4000 m2. The average ACs of 226Ra, 234U, and 238U were 8.3, 13.8, and 17.7 mBq L−1, respectively. The ratios of 226Ra/234U, 226Ra/238U, and 234U/238U were 0.47, 0.6, and 0.79, respectively. A linear correlation was found between ACs and water depth. The ACs predicted by the QWASI (Quantitative Water, Air, Sediment Interaction) model agree with the measured values. [ABSTRACT FROM AUTHOR]

Western Alaska’s convergent margins are composed of tectonostratigraphic terranes. On land, terrane assembly is recognized along boundaries or sutures between neighboring geologic elements with distinctly different origins. In marine areas where rock outcrops are covered by sediment, recognizing terrane sutures is problematic. A fault in seismic dip line 5 of the ALEUT project has been interpreted as a terrane suture. It is imaged intermittently down to the 30+-km-deep plate interface. Processing of ALEUT strike line 7 revealed the suture at ~18 km depths extending 300 km along the margin. Upper structures in line 5 are like the structures of adjacent seismic transects where imaging is only 8−10 km deep. They were previously not recognized as the upper reaches of terrane sutures and show structural details obscured at greater depths. The composite data are the basis for a simple tectonic model of terrane docking. [ABSTRACT FROM AUTHOR]

The present study investigated a square-shaped group pier with attack angles of 0°, 10°, 15°, 20°, and 30° and spacing of 2, 3, and 4 times the pier width and a single pier with the same attack angles in the same experimental conditions. Also, a semi-empirical equation was presented for predicting the maximum depth of scour for single pier and group pier, which had good agreement with experimental results. Results indicated that by considering the angle of the single square pier, the flow impact area on the pier was altered, and the maximum depth of scour was reduced due to deformation resulting from the attack angle of the pier. In the tests related to the group pier, the attack angle of 15° was known as the critical attack angle in this study, which agreed with the results of previous studies. [ABSTRACT FROM AUTHOR]

The ocean is the largest active carbon reservoir on Earth. Organic carbon (OC), as the primary species of carbon sequestration in the ocean, plays an important role in the global carbon cycle through its deposition and burial. In this study, sedimentary OC data from 5796 stations, together with relevant geochemical and sedimentological parameters in the Bohai Sea, Yellow Sea, and East China Sea (BYES) were used to summarize and elucidate the distribution and burial patterns of sedimentary OC, and assess carbon sink effect of sedimentary OC burial. The results show that the OC content in the sediments of the BYES ranges from 0.00% to 2.12%, with an average content of 0.47%±0.26%. OC content is significantly correlated with finegrained sediments, with an average OC content in mud areas being 39% higher than that in non-mud areas. Modern OC buried in the BYES are mainly deposited in 7 major mud areas, with a total sedimentary OC burial flux of approximately 8.20 Mt C yr−1. Among them, the burial flux of biospheric OC is 6.92 Mt C yr−1, equivalent to the OC consumption amount of silicate weathering of the 9 major river basins in the eastern China. In its natural state, the annually sequestered OC in the sediments of the eastern China seas is equivalent to 25.37 Mt of atmospheric CO2, indicating a significant carbon sink effect. The distribution and burial of terrigenous OC in the BYES are mainly influenced by the large river inputs and complex marine hydrodynamic environment, while human activities such as dam construction have significantly altered the OC burial in these coastal mud areas. [ABSTRACT FROM AUTHOR]

Intensive winter grazing on forage crops helps overcome winter feed shortages but is associated with soil pugging and high rates of sediment and nutrient losses. A recently recommended approach to intensive winter grazing management–grazing from the top of the slope downwards (‘top-down’)–can substantially reduce sediment and nutrient losses as part of a suite of practices called ‘strategic grazing’. We hypothesised that this new management has had significant uptake and that a farmer’s risk preferences, values, and demographics influence adoption of these practices. Using a national-scale survey of farmers from 2023, we found that 52.5% of respondents who grazed winter forage crops on slopes, grazed top-down. Location had a modest impact on this decision, with Otago respondents being 17–24% more likely to graze top-down than those from other regions. Māori farmers were 30% more likely to graze top-down than non-Māori farmers. Profitability was positively correlated with this decision. We conclude that the adoption of top-down grazing practices on slopes for winter forage crops is widespread, with just over half of the farmers surveyed grazing winter forage crops top-down. [ABSTRACT FROM AUTHOR]

Fluvial networks are characterised by spatial and temporal transitions as geomorphic and ecological processes within these systems are mediated longitudinally by sediment and water fluxes which vary spatially in magnitude and variability. The aim of this special issue was to shed light on the nature of source-to-sink fluvial transitions associated with spatial and temporal variability in geomorphic and hydrological processes. We encouraged contributions that considered fluvial transitions at any spatial or temporal scale, and invited research that addressed the implications of such transitions. The number of submissions was limited, which was potentially indicative of the lack of field-based studies being conducted at a catchment- or source-to-sink scale. Two of the published submissions considered longitudinal transitions in sediment sources using a sediment finger-printing approach, while the remaining two articles combined traditional fluvial sedimentology techniques with optically stimulated luminescence chronology to deduce controls on river reach flood dynamics. As we enter a time of unprecedented human impact on the environment, there is a clear need for future research to focus on the catchment as a holistic unit as the interconnectedness of landscape pattern and process has implications for biodiversity, water quality, ecosystem service provision and thus catchment management. [ABSTRACT FROM AUTHOR]

The results of regional studies of Early Miocene deposits in Western Ciscaucasia, based on the seismic stratigraphic analysis, are presented. The spatial pattern of sediment accumulation is analyzed and the paleogeographic conditions during the Late Miocene regressive stages in Western Ciscaucasia are refined. Erosional incisions of several levels, developed during the base-level fall in the course of major regressions in the studied time interval, were identified. Based on the spatial correlation of paleoincisions using a chosen series of intersecting seismic profiles, the buried Paleo-Don and Paleo-Donets river valleys were reconstructed at the Sarmatian‒Meotian boundaries and within the Meotian‒upper Pontian interval. [ABSTRACT FROM AUTHOR]

To reveal the enrichment conditions and resource potential of coal-rock gas in the Ordos Basin, this paper presents a systematic research on the sedimentary environment, distribution, physical properties, reservoir characteristics, gas-bearing characteristics and gas accumulation play of deep coals. The results show that thick coals are widely distributed in the Carboniferous-Permian of the Ordos Basin. The main coal seams Carboniferous 5# and Permian 8# in the Carboniferous-Permian have strong hydrocarbon generation capacity and high thermal evolution degree, which provide abundant materials for the formation of coal-rock gas. Deep coal reservoirs have good physical properties, especially porosity and permeability. Coal seams Carboniferous 5# and Permian 8# exhibit the average porosity of 4.1% and 6.4%, and the average permeability of 8.7×10-3 µm2 and 15.7×10-3 µm2, respectively. Cleats and fissures are developed in the coals, and together with the micropores, constitute the main storage space. With the increase of evolution degree, the micropore volume tends to increase. The development degree of cleats and fissures has a great impact on permeability. The coal reservoirs and their industrial compositions exhibit significantly heterogeneous distribution in the vertical direction. The bright coal seam, which is in the middle and upper section, less affected by ash filling compared with the lower section, and contains well-developed pores and fissures, is a high-quality reservoir interval. The deep coals present good gas-bearing characteristics in Ordos Basin, with the gas content of 7.5-20.0 m3/t, and the proportion of free gas (greater than 10%, mostly 11.0%-55.1%) in coal-rock gas significantly higher than that in shallow coals. The enrichment degree of free gas in deep coals is controlled by the number of macropores and microfractures. The coal rock pressure testing shows that the coal-limestone and coal-mudstone combinations for gas accumulation have good sealing capacity, and the mudstone/limestone (roof)-coal-mudstone (floor) combination generally indicates high coal-rock gas values. The coal-rock gas resources in the Ordos Basin were preliminarily estimated by the volume method to be 22.38×1012 m3, and the main coal-rock gas prospects in the Ordos Basin were defined. In the central-east of the Ordos Basin, Wushenqi, Hengshan-Suide, Yan'an, Zichang, and Yichuan are coal-rock gas prospects for the coal seam #8 of the Benxi Formation, and Linxian West, Mizhi, Yichuan-Huangling, Yulin, and Wushenqi-Hengshan are coal-rock gas prospects for the coal seam #5 of the Shanxi Formation, which are expected to become new areas for increased gas reserves and production. [ABSTRACT FROM AUTHOR]

Earthquake recurrence intervals, surface-rupture extents, and interactions between faults provide insight into how faults behave and are critical for seismic hazard mitigation and earthquake forecasting. Investigating the paleoseismology of spatially related faults can reveal strain distribution and whether faults rupture as a system or independently. Summer Lake basin, a graben in the northwestern Basin and Range with four active faults (three of which have prior paleoseismic investigations), provides an opportunity to investigate fault interactions. To expand the paleoseismic record, two trenches were excavated across the previously undocumented Thousand Springs fault, exposing a normal fault zone that offsets a sequence of deep- to shallow-water lake sediments, sand dunes containing reworked Mazama ash, and other Cascades-sourced tephra. Tephra units were correlated to known units by their physical characteristics, stratigraphic sequence, glass chemistry, and two new radiocarbon dates from the uppermost lake sediments. Using trench exposures, measured vertical separations through auguring, colluvial wedges, and extrapolated offsets based on a constant sedimentation rate, we identified at least five surface-rupturing earthquakes with a total offset of 3.4 + 2/-1 m in the past ~65 ka. The oldest event (EH5) occurred at 63.8 ± 1.5 ka, event horizon 4 at 36.2 ± 12.7 ka (which could be more than one event), and event horizon 3 at 24.6 ± 0.3 ka. Event horizon 2, a warping event at our site, is likely more than one event and occurred between 7.5 and 10 ka; and the most recent event (EH1+), most likely more than one event, occurred between 3.3 and 7.7 ka. Several events correlate, within error, with events on other faults in the Summer Lake basin, suggesting that (1) the faults generally rupture together as a system, (2) the most recent earthquake may have ruptured all faults in the region, and (3) fault rupture is influenced by the rapid regression of Lake Chewaucan (~13 ka). [ABSTRACT FROM AUTHOR]

The accurate prediction of Darcy‐scale permeability (absolute permeability and gas‐water relative permeability) of hydrate‐bearing sediments (HBS) plays a crucial role in assessing reservoir potential and optimizing recovery strategies. However, the challenges of field coring, the rigorous conditions encountered in laboratory permeability tests, and the multi‐scale pore structure characteristics of HBS complicate the understanding of the relationship between pore structures and Darcy‐scale permeability of HBS. In this study, we propose an innovative upscaling method that integrates flow properties of typical regions, such as coarse, medium, and fine regions, to predict the Darcy‐scale permeability of HBS from the pore‐scale. This method considers two hydrate habits (pore‐filling and grain‐coating hydrates), heterogeneity and anisotropy of HBS, and multi‐scale pore structures. Taking the absolute permeability of hydrate‐free sediments in the y direction for example, the permeability values for the fine region, the medium region, the coarse region, and the equivalent HBS are 9.43 D, 13.59 D, 18.87 D, and 14.06 D, respectively. Thus, the predicted permeability (14.06 D) is much closer to the experimental data (15.44 D), which validates the efficacy of our upscaling method in estimating Darcy‐scale permeability. Moreover, the characteristics of our predicted Darcy‐scale permeability align with those reported in previous literature. This approach introduces a groundbreaking perspective for predicting permeability in HBS from pore‐scale to Darcy‐scale. It offers essential insights into predicting permeability in HBS while effectively preserving the impact of pore‐scale structural variations caused by local heterogeneity and facilitating numerical simulations of gas production from hydrate reservoirs. Key Points: An innovative upscaling method is proposed to predict the Darcy‐scale permeability of hydrate‐bearing sedimentsThe predicted permeability exhibits good agreement with test dataThe proposed method allows predicting Darcy‐scale permeability while preserving the effects of micro‐pore structure variation [ABSTRACT FROM AUTHOR]

Periodic outbreaks of crown‐of‐thorns starfish have led to severe coral reef degradation, with one hypothesized cause being eutrophication. Phosphorus (P) is one of the driving factors for eutrophication, but researches on the spatiotemporal distributions of P in coral reefs are limited, impeding our understanding of the P cycling in coral reefs and its correlation with starfish outbreaks. This study undertook an analysis of various P species, migration and transformation in seawater, sediments, and crown‐of‐thorns starfish within the coral reefs of the Xisha Islands, northern South China Sea. The results show that in seawater, P predominantly existed in the dissolved phase, with organic P constituting the largest fraction (>67%). Conversely, in sediments, P primarily existed as inorganic form (43%−95%), with calcium‐bound P comprising the majority (26%−46%). Notably, exchangeable P accounted for a relatively smaller fraction (9%−20%) but played a significant role as a source of P released from sediments into seawater (0.01−0.17 mmol m−2 hr−1). During starfish outbreaks, starfish (1,000 individuals per hectare) assimilated P from seawater via phytoplankton or corals, resulting in substantial accumulation of both organic and inorganic P in their tissues (69−315 μmol g−1). Meanwhile, starfish excretion released P back into the seawater, which contributes to the migration and transformation of various P forms. Historical data also show a close relationship between P content and starfish density. These findings highlight the interactions between starfish and P cycling within coral reefs, and provide valuable insights into conservation and restoration on coral reefs, especially those severely affected by starfish outbreaks. Plain Language Summary: The coral reefs of the Xisha Islands, northern South China Sea have experienced periodic outbreaks of crown‐of‐thorns starfish, causing severe degradation of the coral reefs. However, the reasons for the outbreak of starfish remain unclear. This study aims to investigate the relationship between P content and starfish outbreaks, and examines where and how P migrates and transforms in seawater, sediments, and crown‐of‐thorns starfish. This study discovered that the majority of P in seawater existed in a dissolved state, primarily as organic compounds. In sediments, P existed mostly in inorganic forms, particularly bound to calcium, which is commonly found in coral reef sediments. The proportion of exchangeable P which can easily migrate from the sediments into the seawater was the least. During starfish outbreaks in the Xisha Islands, the density of starfish can hit 1,000 individuals per hectare. These starfish assimilated P from seawater via phytoplankton or corals, resulting in significant amounts of both organic and inorganic P within their tissues. Yet, starfish excretion releases P back into the seawater. This study linked starfish outbreaks to DIP levels, which helps us understand the P cycling in coral reefs and provides some outlooks on coral reef conservation in the context of starfish outbreaks. Key Points: Water P in Xisha's coral reefs mainly existed in DOP, as a significant DIP source via degradationPorous calcium carbonate boosted Ca‐P and Ex‐P proportion and DIP release in reef sedimentsCrown‐of‐thorns starfish stored and released OP and IP, affecting P cycle and starfish outbreaks [ABSTRACT FROM AUTHOR]

The navigation waterways to the harbors of Rostock (Warnow Estuary), Germany, and Szczecin (Oder/Szczecin Lagoon), Poland, were recently deepened. Both activities required Environmental Impact Assessments. We conducted expert- and data-based ecosystem service assessments for both case studies. Additionally, we performed 3D-ecosystem model simulations. For the Oder Lagoon, the model results show that the waterway deepening increased the burial in sediments by 807 t N/a, 112 t P/a and 4661 T C/a. However, altogether, the impacts of the deepening to 12.5 m draught on the lagoon ecosystem are minor and a model application is not necessary, but the results improve the data basis for ecosystem service assessments. Our expert-based ecosystem service approach is adaptable to the needs of coastal engineering and hydraulic projects and is both easy and quick to apply and transferable. The assessment results highlight the relevance of cultural services and can complement EIAs. Our approach can especially support the early scoping stage of an EIA. It has the potential to enhance cooperation and communication with and between stakeholders, reduce conflicts, and save time. Additionally, it could improve the compilation and addressing of stakeholder concerns, potentially reducing costs associated with unnecessary studies. [ABSTRACT FROM AUTHOR]

Purpose: Straw fiber (SF) is a natural and environmentally friendly material, which has great potential in improving the hydro-mechanical behavior of cemented dredge sediment. However, the treatment mechanisms and optimum application dosage of SF in cemented sediment at high water content are unclear. This study investigates the effect of SF on the shear strength and permeability of cemented sediment at high water content (3 times the liquid limit). Methods: Various SF contents (0%, 0.3%, 0.5%, 1%, 3%, 5%, 8% and 12% by mass) and curing ages (3, 7, 14, 28, 60, 90, 180 days) were considered to improve cemented dredged sediment. The effectiveness of the improvement was evaluated through unconfined compression and permeability tests. Results: The test results show that there is an optimum SF content of 0.5%, below which the unconfined compression strength (qu) of SF-reinforced cemented sediment (SFCS) increased with SF content. Beyond this point, qu decreased with SF content. The brittleness index (Ib), which indicates the ductility behavior, increased with SF content across the entire SF range (0–12%). When SF addition was relatively low (< 0.5%), pore filling and bridge effects increased the interface force between SF and sediment particles, resulting in positive effects on the improvement of SFCS strength. However, when SF content exceeded 0.5%, the higher organic matter from SF could suppress pozzolanic reaction, leading to weaker cemented bonding between sediment particles and hence lower sediment strength. Conclusion: This study suggests that 0.5% SF should be applied in cemented dredged sediment at high water content to optimize its strength. [ABSTRACT FROM AUTHOR]